Offshore support structure method and apparatus
FIELD OF THE INVENTION 
     The invention relates to offshore support structure methods and apparatus for use with wells located in a body of water, the wells having an upstanding conductor pipe extending from the ground below the body of water to above the surface of the water. 
     DESCRIPTION OF THE PRIOR ART 
     Typically in wells completed at offshore locations, the well has been drilled from a jackup drilling rig or a semi-submersible drilling rig, and the vessel which supports the drilling rig typically remains on location during the drilling process. When the drilling vessel is subsequently moved to another location, the well is typically left with suitable casing in the borehole extending to some selected depth and production tubing is also typically installed. A conductor pipe typically surrounds the casing and extends into the ground below the body of water and it typically extends upwardly beyond the surface of the water a distance of between 15 and 45 feet, or perhaps higher. The conductor pipe may have a diameter from 30 to 100 inches. The water depth may be from 40-50 feet to 200-250 feet deep, which are considered relatively shallow offshore depths. 
     The well is typically shut in by installing suitable closed valves or plugs in the well, and the conductor pipe is thus left unsupported, extending from the ground beneath the body of water to above the surface of the water. In order to produce hydrocarbons from the well, it is necessary that some type of platform structure, such as a production platform, be installed above the well in order that the hydrocarbons from the well can be produced. As is conventional in the art, well production equipment is typically installed upon the production platform at the well. In some instances, the production platform is fabricated as an integral unit on shore and then towed to the location of the well and installed. Such integral production platforms are not fabricated quickly and they must be designed and fabricated to exactly conform to the particular water depth and soil conditions and elevations present at the site of the offshore well. Accordingly, the exposed and unsupported conductor pipe can be unprotected and unsupported for a period of time which can be from twelve to eighteen months until after the completion of the well, at which time the totally fabricated production platform is ready for installation at the offshore well. During that period of time the free-standing conductor pipe is vulnerable to damage from navigating ships in the area, and it can also be damaged by forces exerted by the body of water caused by severe weather conditions such as winter storms and/or summer hurricanes. It is thus susceptible to bending and damage when left unprotected. Accordingly, it would be desirable to economically and efficiently support the conductor pipe to protect it until such time as a production platform structure can be permanently installed. 
     In view of the high cost of the typical permanent production platform, which is typically fabricated as an integral unit and installed at the offshore well, it would be desirable if a support structure for supporting the conductor pipe could also be utilized to either assist in supporting a platform structure, or to provide enough support to the conductor pipe, so that the conductor pipe could support a platform structure disposed upon the conductor pipe. Such double duty by the support structure would greatly reduce the costs associated with the production platform. By reducing the costs of placing the well into production, it is thus possible that some less productive, or marginal, offshore wells could be placed into production of hydrocarbons. 
     Such a support structure for the conductor pipes of offshore wells has been previously proposed and utilized as disclosed in U.S. Pat. No. 4,558,973. However, it is believed that such a support structure has presented some problems. This prior art support structure utilizes a clamp structure to secure the support structure to the conductor pipe and the clamp structure extends from the ground below the body of water upwardly over and along a substantial portion of the length of the conductor pipe disposed under the surface of the water. This clamp structure utilizes a plurality of bolts extending along its length, which bolts must be tightened by divers at the time of installation of the support structure. Further, at least four piles must be driven to secure the support structure to the round below the body of water. Thus, an extensive amount of time and energy is required in installing such a support structure, particularly with respect to the great number of bolts which must be secured. Such bolts require the services of an underwater diver to complete the bolt fastening step, as well as the time and effort necessary to drive the four piles. 
     Accordingly, prior to the development of the present invention, there have been no offshore support structure methods and apparatus for use with conductor pipes of offshore wells which: are simple and economical to manuufacture and use; are easily assembled; require a minimum amount of work to be performed by underwater divers; and require a minimum number of piles to be driven into the ground beneath the body of water. 
     Therefore, the art has sought offshore support structure methods and apparatus for use with conductor pipes of offshore wells which: are simple and economical to manufacture and use; are easily assembled; require a minimum amount of work by underwater divers; and require a minimum number of piles to be driven into the ground beneath the body of water. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, the foregoing advantages have been achieved through the present support structure for use with an offshore well located in a body of water, the well having an upstanding conductor pipe, having upper and lower ends, extending from the ground below the body of water to above the surface of the water. The present invention includes: two tubular legs, each leg having upper and lower ends and adapted to extend from the ground to at least the surface of the water; a pile skirt fixedly secured to each of the two legs at the lower end of each of the two legs; and means for pivotably connecting the upper ends of each of the two legs to the conductor pipe, the two legs being radially spaced from one another; the pivotal connection means being adapted to be disposed upon the conductor pipe at least at the surface of the water or higher, whereby the two legs and pivotal connection means can be secured at their upper ends to the conductor pipe and the lower ends of the legs can be pivoted downwardly into contact with the ground. A further feature of the present invention is that a platform structure may be disposed upon the conductor pipe. 
     The present invention also includes a method for supporting an upstanding conductor pipe of a well located in a body of water, the conductor pipe having upper and lower ends and extends from the ground below the body of water to above the surface of the water. This aspect of the present invention includes the steps of: floating in the water two legs, each leg having upper and lower ends, and a pile skirt fixedly secured to each of the two legs at the lower end of each leg; disposing the upper ends of each leg adjacent the portion of the conductor pipe extending above the surface of the water; pivotably connecting the upper ends of each of the two legs to the conductor pipe at the surface of the water or at a location upon the conductor pipe higher than the surface of the water; pivoting each of the legs downwardly until the pile skirt of each leg contacts the ground; and driving a single pile through each pile skirt to fixedly secure each leg to the ground, whereby the conductor pipe is supported toward its upper end within the body of water. Another feature of the present invention is the step of disposing a platform structure upon the conductor pipe, the platform structure being fixedly secured to only the conductor pipe. 
     The offshore support structure methods and apparatus for use with a well having an upstanding conductor pipe of the present invention, when compared with previously proposed prior art offshore support structure methods and apparatus, have the advantages of: being simple and economical to manufacture and use; are easily assembled; require a minimum amount of time and effort being spent by underwater divers; and require a minimum number of piles to be driven into the ground beneath the body of water. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawings: 
     FIG. 1 is a side view of a support structure in accordance with the present invention; 
     FIG. 2 is a top view of the support structure of FIG. 1; and, 
     FIG. 3 is a side view of the support structure of FIG. 1, illustrating a platform structure being supported by the conductor pipe. 
     While the invention will be described in connection with the preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 1-3, a support structure 200 in accordance with the present invention is shown in use with a well 201 located in a body of water 202, the well 201 having an upstanding conductor pipe 203, having upper and lower ends 204, 205, extending from the ground 206 below the body of water 202 to above the surface of the water 202. Support structure 200 generally includes two tubular legs 207, each leg 207 having upper and lower ends 208, 209; a pile skirt 250 fixedly secured to each of the two legs 207, at the lower end 209 of each of the two legs 207; and means for pivotably connecting 251 the upper ends 208 of each of the two legs 207 to the conductor pipe 203. 
     As will be hereinafter described in greater detail, upon legs 207 being pivoted downwardly, as shown in dotted lines in FIG. 3, into engagement with ground 206, each tubular leg 207 extends from the ground 206 to at least the surface of the water 202 and preferably above the surface of the water 202, as seen in FIGS. 1 and 3. As seen in FIG. 2, each of the two legs 207 are radially spaced from one another. The pivotal connection means 251 is preferably disposed upon the conductor pipe 203 at a location at least at the surface of the water 202 and preferably above the surface of the water 202, as shown in FIGS. 1 and 3. 
     Preferably, pivotal connection means 251 preferably includes a hook member 252, adapted to be fixedly secured to the conductor pipe 203 as by welding, for each leg 207, which hook members 252 are radially spaced about the conductor pipe 203, as seen in FIG. 2. Each hook member 252 is associated with the upper end 208 of a leg 207, whereby legs 207 are freely pivotable with respect to conductor pipe 203, about hook members 252 and pivot pins 253 associated with the upper ends 208 of legs 207. Preferably, the hook members 252 are each formed of two hook-shaped plate members 230 attached to, or formed integral with, a base plate member 231, base plate member 231 being secured to conductor pipe 203, as by welding, as seen in FIG. 2. The upper end 208 of each leg 207 preferably has a plate member 232 extending therefrom which has a pivot pin 253 fixedly secured thereto, as by welding, and passing therethrough, as seen in FIG. 2. Alternatively, as will be readily seen by one of ordinary skill in the art, other pivotal connections, such as a hook and eye connection or other pivot pin joints, could be utilized for pivotal connection means 251. 
     A means for securing 234 each leg 207 to conductor pipe 203 may be associated with the upper end 208 of each leg 207. Preferably each securing means 234 comprises a slidable sleeve 235 disposed upon the upper end 208 of each leg 207. The upper end 236 of each sleeve 235 preferably has a rounded and tapered configuration, whereby after leg 207 has been pivoted downwardly, as shown in FIG. 3, sleeve 235 may be moved upwardly to abut conductor pipe 203 in a close fitting, abutting relationship with the conductor pipe. Preferably, sleeve 235 is then fixedly secured to conductor pipe 203, as by welding, and sleeve 235 may also be secured, as by welding, to the upper end 208 of leg 207, as seen in FIGS. 2 and 3. Securing means 234 then serves to relieve stresses and strains exerted upon pivotal connection means 251, as well as, protect pivotal connection means 251 from the elements in order to reduce corrosion thereof. Alternatively, after leg 207 is pivoted downwardly into the position shown in FIG. 3, pivotal connection means 251, or hook members 252 and pivot pins 253 can be fixedly secured to one another as by welding to maintain the relative position of legs 207 with respect to conductor pipe 203, as shown in FIGS. 2 and 3. 
     Preferably, each pile skirt 250 has a conventional mud mat 254 fixedly secured thereto. Mud mats 254 are provided to pile skirts 250 to prevent them from sinking into potentially soft ground 206 before piles 221 (FIG. 3) can be driven through pile skirts 250. Each pile skirt 250 is fixedly secured to the lower end 209 of legs 207 as by welding as shown at 245. 
     Still with reference to FIGS. 1-3, the method for supporting an upstanding conductor pipe 203 of a well 201 located in a body of water 202 will be described. The method generally comprises the steps of: transporting, as by floating in the water, two legs 207; disposing the upper ends 208 of each leg 207 adjacent the portion of the conductor pipe 203 extending above the surface of the water 202; pivotably connecting the upper ends 208 of each of the two legs 207 to the conductor pipe 203 at the surface of the water 222, or at a location upon the conductor pipe 203 higher than the surface of the water 202; pivoting each of the legs 207 downwardly until the pile skirt 250 of each leg 207 contacts the ground 206; and driving a single pile 221 through each pile skirt 250 to fixedly secure each leg 207 to the ground 206, whereby the conductor pipe 203 is supported toward its upper end 204 within the body of water 202. The method further preferably includes the step of circumferentially disposing a mud mat 254 about each pile skirt 250. The method may further preferably include the steps of pivotably connecting the upper ends 208 of each leg 207 to the conductor pipe 203 by disposing two hook members 252 radially spaced about the conductor pipe 203, each hook member 252 engaging a pivot pin 253 associated with the upper end 208 of each leg 207. With reference to FIG. 3, it is seen that the method may further include the step of disposing a platform structure 244 upon the conductor pipe 203, the platform structure 244 being fixedly secured to only the conductor pipe 203. 
     The method may further include the step of securing the upper end 208 of each leg 207 to the conductor pipe 203, which step may be accomplished by sliding upwardly a sleeve 235 disposed upon the upper end 208 of each leg 207 into an abutting and mating relationship with conductor pipe 203 and welding sleeve 235 to the conductor pipe 203 and the leg 207. 
     It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials or embodiments shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art; for example, the various pivotal connection means could be universal joints. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.